DESCRIPTION (Verbatim from the Applicant's Abstract): Synaptic plasticity plays an important role in a number of fundamental processes in all higher organisms including development, regeneration, learning and memory. The goal of this application is to identify genes/signal transduction pathways important in regulating central synaptic plasticity, using Drosophila as a simple model system. Studies at the NMJ in Drosophila have demonstrated that a number of mutants identified on the basis of learning and memory deficits, define genes that are important in regulation of transmission and plasticity at the peripheral glutaminergic synapse. However, limited electrophysiological access to neurons in the adult fly CNS has precluded assessment of the role of these genes in regulating central synaptic transmission. This application makes use of dissociated cell cultures in which spontaneously active, excitatory cholinergic synapses form between primary embryonic Drosophila neurons, providing the first opportunity to explore the functional properties of transmission at central synapses in this organism. Electrophysiological studies will be used to identify mutations that disrupt one or more aspects of cholinergic synaptic transmission. Structural and molecular studies in mutant and wild type neurons will be important in further defining the underlying mechanisms regulating synaptic transmission during development and in differentiated neurons. The principal investigator's preliminary data demonstrates altered transmission at cholinergic synapses in dunce, a learning and memory mutant with defects in cAMP-signaling. Biochemical studies in differentiated wild type neurons have revealed that cAMP-dependent plasticity at central cholinergic synapses is likely to be important in experience-dependent memory formation in Drosophila. The use of protein/RNA synthesis inhibitors and transgenic flies to regulate dCREB2 expression are proposed to examine the mechanisms involved in cAMP-dependent plasticity at these synapses. Identification of additional genes that are important in regulation of transmission will focus on learning and memory mutants that have not been directly linked to the cAMP-signaling pathway (latheo, leonardo). The results of the studies will provide the first insights into the cellular and molecular mechanisms of central synaptic plasticity in Drosophila. The contribution of these studies to the principal investigator's general understanding of synaptic plasticity, likely to be highly conserved between vertebrates and invertebrates, will be useful in designing treatments aimed at regulating synaptic function disrupted by developmental disorders, disease, injury or during normal aging in humans.